Amine compounds have heretofore been used for various applications, for example, as intermediates for the production of various drugs or pigments, as charge transport materials for organic electroluminescent elements, as curing agents for epoxy resins, and as functional materials including catalysts for the production of polyurethanes. Among them, 1,4-diazabicyclo[2.2.2]octane (hereinafter referred to simply as “TEDA”) being a cyclic amine compound, has a strong nucleophilicity and is widely used as a basic catalyst for various organic reactions, particularly as a general-purpose gelling catalyst in the field of polyurethane resins.
A polyurethane resin is usually produced by reacting a polyol and a polyisocyanate in the presence of a catalyst and, as the case requires, a blowing agent, a surfactant, a flame retardant, a cross-linker, etc. For the production of polyurethane resins, many metal-type compounds or tertiary amine compounds are used as catalysts. They are used alone or in combination industrially frequently.
In the production of polyurethane foams wherein water, a low boiling point organic compound or both of them are used as a blowing agent, among such catalysts, tertiary amine compounds are particularly widely used, since the productivity and formability are thereby excellent. Such tertiary amine compounds include, in addition to the above-mentioned TEDA, e.g. N,N,N′,N′-tetramethyl-1,6-hexanediamine, bis(2-dimethylaminoethyl)ether, N,N,N′,N″,N″-pentamethyldiethylenetriamine, N-methylmorpholine, N-ethylmorpholine, N,N-dimethylethanolamine, etc. (e.g. Non-patent Document 1). As the metal-type catalysts, organic metal compounds such as organic tin compounds are, for example, frequently used, but as the productivity or formability is thereby deteriorated, they are rarely used alone, and in most cases, they are used in combination with a tertiary amine catalyst.
Among them, the tertiary amine compounds are gradually leaked as volatile amines from polyurethane products and are likely to cause, e.g. in the case of interior parts for automobiles, etc., an odor problem or a discoloration problem of other materials (e.g. PVC leather) by the volatile amines. Further, the tertiary amine catalysts usually have a strong odor, whereby the working environment is seriously deteriorated under the production of polyurethane resins. As a method to solve such problems, it has been proposed to use, instead of such volatile tertiary amine catalysts, amine catalysts (so-called “reactive catalysts”) having a hydroxy group or a primary or secondary amino group reactive with a polyisocyanate in their molecules, or bifunctional cross-linkers having a tertiary amino group in their molecules (e.g. Patent Documents 1 to 6).
According to the above Patent Documents, such amine compounds are fixed in the polyurethane bond network by reacted with polyisocyanates, whereby the above problems can be avoided. Such a method can be regarded as a method effective to reduce the odor of the final resin products.
However, such amine catalysts are poor in the activity for the gelling reaction (the reaction of a polyol and an isocyanate), and thus, there is a problem such that the curing properties of polyurethane resins tend to be low. Whereas, the method of using the above cross-linkers is effective to reduce the odor of the final polyurethane resin products and to improve the working environment at the time of the production of the polyurethane resins, but the physical properties such as the hardness of the polyurethane resins tend to be thereby inadequate.
On the other hand, the metal-type compounds do not cause the odor problem or the problem to deteriorate other materials like the above-mentioned tertiary amine catalysts. However, if a metal-type compound is used alone, the productivity, physical properties, moldability, etc., tend to deteriorate, and among metal-type catalysts, there are ones containing a heavy metal such as lead, tin, mercury or the like, which are likely to cause a toxicity problem or an environmental problem due to the heavy metal remaining in the products.
Under the circumstances, the applicants have already filed patent applications (e.g. Patent Documents 7 and 8) relating to a process for producing a polyurethane resin by using 2-hydroxymethyltriethylenediamine as a catalyst. However, it is necessary to suitably select a catalyst to be used, depending upon the particular purpose of a polyurethane resin product, and it is further desired to develop a process for producing a polyurethane resin without using a catalyst containing a heavy metal.
Further, 1,5-diazabicyclo[3.2.2]nonane being a cyclic amine compound has been proposed as a catalyst for producing a polyurethane resin (e.g. Patent Document 9), and its physical properties are reported in Non-patent Document 2. However, there has been no report with respect to a 3-hydroxy-1,5-diazabicyclo[3.2.2]nonane having a hydroxy group introduced to a specific position of 1,5-diazabicyclo[3.2.2]nonane.